The sun's core is overwhelmingly composed of helium and hydrogen, with about 1% oxygen and about %1 everything else. At least according to the standard model, I don't know how much "wiggle room" there is in our understanding

https://en.wikipedia.org/wiki/Solar_core

At the edge of the core is about 70% hydrogen 28% helium with the helium fraction increasing up to 66% right at the center.

One thing I think you're missing is how overwhelmingly the cloud that formed the solar system was hydrogen and helium.

https://en.wikipedia.org/wiki/Formation_and_evolution_of_the...

The gas cloud that formed the solar system is expected to have been 98% hydrogen and helium, 2% everything else. We don't see these ratios on rocky planets like earth because the gravity here isn't strong enough to hold the hydrogen and helium, so mostly it escaped and we have a wildly non-representative sample of elements left.